Rosene, D. L. | bioRxiv Science

bioRxiv2024

Mesenchymal Cell-Derived Extracellular Vesicles Ameliorate Age-Related Deficits in Working Memory as well as Brain MRI and CSF in vivo Biomarkers of Neurodegeneration in Rhesus Monkeys.

Normal aging in humans and non-human primates is associated with a decline in cognitive functions. Subject-wise differences in cognitive decline can be attributed to different degrees of damage to cortical white matter (WM) which is largely affected by neuroinflammation during aging. Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) have recently been identified as a potential immunomodulatory therapeutic for brain damage and Alzheimers disease (AD) and related dementias by suppressing neuroinflammation. Here, we evaluated the efficacy of MSC-EVs for slowing or ameliorating cognitive decline during aging in rhesus monkeys, a well-studied model of normal aging that is free of extensive AD pathology. We report that late middle-aged monkeys treated with MSC-EVs every two weeks for 18 months showed improved performance on a task of spatial working memory relative to vehicle control monkeys. In addition, we used diffusion magnetic resonance imaging (MRI) and resting state functional MRI to evaluate structural white matter and functional network changes in vivo. Imaging data revealed that MSC-EV treatment preserved prefrontal and temporal WM structural integrity and large-scale functional network connectivity that are correlated with early, increased CSF levels of amyloid beta protein. Amyloid beta levels at 12 months are also correlated with improved cognitive performance at the end of the 18 months of treatment. These findings suggest that MSC-EVs can mitigate age-related cognitive decline by potentially enhancing the CSF clearance of neurodegenerative proteins, which correlates with greater WM integrity and functional brain connectivity.

neuroscience↗

bioRxiv2023

Neuronal properties of pyramidal cells in lateral prefrontal cortex of the aging rhesus monkey brain are associated with performance deficits on spatial working memory but not executive function.

Age-related declines in cognitive abilities occur as early as middle-age in humans and rhesus monkeys. Specifically, performance by aged individuals on tasks of executive function (EF) and working memory (WM) is characterized by greater frequency of errors, shorter memory spans, increased frequency of perseverative responses, impaired use of feedback and reduced speed of processing. However, how aging precisely differentially impacts specific aspects of these cognitive functions and the distinct brain areas mediating cognition are not well understood. The prefrontal cortex (PFC) is known to mediate EF and WM and is an area that shows a vulnerability to age-related alterations in neuronal morphology. In the current study, we show that performance on EF and WM tasks exhibited significant changes with age and these impairments correlate with changes in biophysical properties of L3 pyramidal neurons in lateral LPFC (LPFC). Specifically, there was a significant age-related increase in excitability of Layer 3 LPFC pyramidal neurons, consistent with previous studies. Further, this age-related hyperexcitability of LPFC neurons was significantly correlated with age-related decline on a task of WM, but not an EF task. The current study characterizes age-related performance on tasks of WM and EF and provides insight into the neural substrates that may underlie changes in both WM and EF with age.

neuroscience↗